Questions Below Are Based on the Following Simulation: a Researcher

Multiple Choice

Questions below are based on the following simulation: A researcher attempted to discover if the amount of learned material retained by first-grade children was a function of the mode by which the material was presented. Two first-grade classes are selected, Miss Emily McKenna's class and 142 Miss Clair Keating's class. The study began at 9 AM on a Monday morning. By a flip of a coin, Mrs. Vivian's class was chosen to receive a visual presentation, whereas in Miss McKenna's class an auditory presentation of the same material was used. One hour later, the two groups were compared regarding the amount of material that was retained.
-The independent variable(s) in this study is (are) the

A) the retention scores.
B) the age of the subjects.
C) the time of testing.
D) the mode of presentation, audio vs. visual.